Arthroscopes and other like optical instruments, such as endoscopes, have long been known in the field of surgery and in other fields. In this application, the invention is described in connection with an arthroscope or similar instrument employed for surgery, as in human surgery.
Over the last fifteen or more years the nature of surgery has changed substantially, with minimally invasive surgery becoming a mainstay. Within the orthopedic community, in particular, arthroscopy and similar techniques have become the most common surgical procedures. Surgery using such techniques is less painful for the patient and, in most instances, can be performed more quickly and safely than with techniques that require greater invasion of the patient""s body; anesthesia is also less complicated, the surgery can often be handled on an outpatient basis, and the procedures are more cost effective. Patients return to normal life more quickly, and hospital stays may be reduced in length or even eliminated. However, all of these benefits are available only if the minimally invasive surgery allows for better diagnostic capabilities, improved surgical techniques, and reduced iatrogenic damage. Similar benefits are available with other, non-surgical, instruments.
One problem in these minimally invasive techniques derives from limitations in the arthroscopes, endoscopes and other principal optical instruments employed. In particular, the rather limited field of view afforded by even the best instruments previously commercially available has inhibited progress to at least some extent; available instruments and techniques have not changed dramatically since 1985. A substantial improvement in the field of view available to a person employing an arthroscope or like instrument for exploratory or repair procedures is much needed.
Several techniques for modification (widening) of the view offered by arthroscopic/endoscopic instruments have been proposed, but they have not been especially successful. Generally, such proposals have required packing a plurality of movable lenses or prisms into the input end of the instrument; the resulting problems of precision of construction, precision of relative movements, space requirements, optical distortions, and elimination of undesired xe2x80x9cambientxe2x80x9d light have been substantial. This is not particularly surprising; interaction between the prisms and lenses involved, along with light loss, exacerbates the problem.
There is a need for an arthroscope that affords the user a broadened effective field of view and that does not require movement of the arthroscope to vary its scope of view. One such arthroscope is disclosed in copending U.S. application Ser. No. 09/243,845, entitled xe2x80x9cVariable View Arthroscopexe2x80x9d and filed Feb. 3, 1999, having a common inventor with the present application. In this specification and in the appended claims the term xe2x80x9carthroscopexe2x80x9d means and should be interpreted to include an endoscope or any other like optical instrument, whether used for surgery or otherwise.
The present invention relates to a variable view arthroscope comprising an elongated housing having an image input end spaced from an outer control end. Lighting is provided for illuminating a working image area beyond the image input end of the housing tube. An input lens, located in the input end of the housing tube, intercepts light reflected back from the working area. The input lens, preferably a diverging type lens, closes (and usually seals) the image input end of the housing tube, which is beveled at an angle of 30xc2x0 to 60xc2x0. The reflected light constitutes a working image and the light image or object rays pass from the working area through the input lens and are directed to a movable mirror. The movable mirror may be rotatable or it may move linearly. There is a control, for example, an elongated control rod, for varying the position of the movable mirror to any position or to a series of fixed positions between a first limit position and a second limit position. A fixed mirror is positioned to intercept light reflected from the movable mirror, redirecting that light toward a relay lens assembly located near the fixed mirror position. The relay lens assembly directs the light image from the fixed mirror through the length of the relay lens assembly to impinge upon a focusing lens assembly. The focusing lens assembly includes a focusing and zoom lens and their controls, and is preferably located in the control portion of the arthroscope.
In an alternative preferred embodiment of the present invention, the input end of the arthroscope includes an input lens, a first mirror, a second mirror and a relay lens assembly. The first mirror is fixed in relation to the input lens but the two move as a unit to alter the view of the arthroscope. The second mirror is movable and directs the image into the relay lens assembly. The input lens and first mirror may rotate about the same axis as the second mirror. As object rays pass through the input lens to the first mirror, to the second mirror and into the relay lens assembly, the length of the axial ray remains the same as the angle of view of the arthroscope changes. The lengths of the rim rays may also remain the same as the angle of view of the arthroscope changes.